Tire Having a Colored Surface

ABSTRACT

A tire includes at least one outer structural element, wherein the at least one outer structural element is at least partially coated by at least one colored coating layer including a colored composition including (a) 5% by weight to 50% by weight with respect to the total weight of the dry colored composition, of at least one crosslinked polymeric compound obtained by reacting (a 1 ) at least one thermoplastic polyurethane with (a 2 ) at least one polyisocyanate; (b) 10% by weight to 80% by weight with respect to the total weight of the dry colored composition, of at least one thermoplastic polymeric compound having a glass transition temperature higher than or equal to 20° C, and (c) 3% by weight to 50% by weight, with respect to the total weight of the dry colored composition, of at least one coloring agent. Preferably, the at least one structural element is at least one of the tire sidewalls.

The present invention relates to a tire having a colored surface, inparticular a colored outer surface.

More in particular, the present invention relates to a tire comprisingat least one outer structural element, said at least one outerstructural element being at least partially coated by at least onecolored coating layer.

Colored compositions intended to cover the outer surface of tires arealready known in the art.

For example, U.S. Pat. No. 3,648,748 relates to a tire comprising acured rubber tire having adhered thereto a laminate of a curedpolyurethane comprising a cured reaction mixture prepared by reacting anorganic polyisocyanate with a reactive hydrogen containing polymericmaterial having a molecular weight of from about 700 to about 5000 and ahydroxyl functionality greater than 2.0 up to about 3.0 selected fromhydroxyl terminated polymers of the group consisting of polymer andcopolymers of 1,3-diene hydrocarbons having 4 to 6 carbon atoms,copolymers of 1,3-diene hydrocarbons having 4 to 6 carbon atoms withstyrene, acrylonitrile, ethyl acrylate and chloro substituted 1,3-dienehydrocarbons having 4 to 6 carbon atoms. The tire is prepared by themethod which comprises (A) cleaning a portion of the surface of a curedrubber tire to be coated with a solvent, (B) coating the said surfacewith the liquid polyurethane reaction mixture and (C) curing the saidreaction mixture to form a composite structure. The abovementionedlaminate is said to be formed on the cured rubber tire withoutpreviously chemically treating the rubber and to provide a decorative,protective or identification surface for the tire.

International Patent Application WO 98/14338 relates to a method ofimprinting markings on rubber articles, more particularly tires, themarking being applied by means of ink and the rubber article comprisingno wax or stabilizer additives in the marking portion, characterized bythe marking being imprinted (for example, by a tampon printing method)and by the ink comprising a binding agent which is adapted to the rubberblend of the marking portion. Preferably, said ink is a solvent-basedtwo component ink comprising from 20% to 35% of coloring pigments and/or2% to 5% vehicle and/or 40% to 60% solvent and/or 15% to 20% bindingagent said binding agent comprising polyurethane resin and polyurethaneprepolymer. Preferably, the ink is cured with aliphatic or aromaticisocyanates. The abovementioned method is said to give good durabilityof the marking on the rubber article. In addition, by eliminating wax orstabilizer additives, there is no risk of the tire or marking in themarking portion becoming discolored.

United States Patent Application 2004/0050471 relates to a tire havingan outer rubber surface based at least in part on essentiallyunsaturated diene elastomers, said outer rubber surface covered with acolored coating bonded thereto, said colored coating having at least onelayer in contact with air and including a composition comprising:

-   (1) a polyurethane in majority proportion; and-   (2) flakes of aluminum in an amount of between 20 and 150 parts of    flakes per hundred parts of dry polyurethane (phr);    wherein the polyurethane is produced from a polyol selected from the    group consisting of aliphatic polyethers, aliphatic polyesters,    polyethers having a main chain that is semi-aromatic and polyesters    having a main chain that is semi-aromatic; and the bond between the    elastomer and colored coating results from interaction of the    polyurethane and polar functions on the elastomer. In fact, said    composition is laid on the vulcanized tire after treatment of the    tire surface to provide reactive polar functions. The abovementioned    colored coating is said to inhibit the degradation due to oxidation    and ozone and greatly limits the migration of the antioxidants    towards the surface of the tire, allowing the rubber composition to    retain its color. Furthermore, the coating prevents the migration of    the waxes towards the surface by a barrier effect, thereby avoiding    efflorescence and retaining its surface appearance.

United States Patent Application 2004/0055680 relates to a tire havingan outer rubber surface based at least in part on essentiallyunsaturated diene elastomers, said outer rubber surface covered with acolored coating bonded thereto, said colored coating having at least onelayer in contact with air and including a composition comprising:

-   (1) a polyurethane in majority proportion; and-   (2) flakes of mica in an amount of between 10 and 80 parts of flakes    per hundred parts of dry polyurethane (phr);    wherein the polyurethane is produced from a polyol selected from the    group consisting of aliphatic polyethers, aliphatic polyesters,    polyethers having a main chain that is semi-aromatic and polyesters    having a main chain that is semi-aromatic; and the bond between the    elastomer and colored coating results from interaction of the    polyurethane and polar functions on the elastomer. In fact, said    composition is laid on the vulcanized tire after treatment of the    tire surface to provide reactive polar functions. The abovementioned    colored coating is said to inhibit the degradation due to oxidation    and ozone and greatly limits the migration of the antioxidants    towards the surface of the tire, allowing the rubber composition to    retain its color. Furthermore, the coating prevents the migration of    the waxes towards the surface by a barrier effect, thereby avoiding    efflorescence and retaining its surface appearance.

According to the Applicant, the colored compositions described above mayhave some disadvantages.

For example, the Applicant has noticed that the application of liquidpolyurethane reaction mixtures (i.e., a liquid reaction mixturecomprising an organic polyisocyanate and a polymeric material containingreactive hydrogen atoms) to the surface of the vulcanized tire which hasto be coated, may cause the release of carbon dioxide which may lead tothe formation of defects on the coated surface with a consequent poorappearance of the same. On the other end, the Applicant has noticed thatthe use of colored compositions comprising polyurethanes may showdiscoloration problems due to the surface migration of antioxidants,antiozonants and waxes usually present in the elastomeric compositions,in particular in those used in tire manufacturing. Moreover,difficulties have been encountered in obtaining a good adhesion betweencolored compositions comprising polyurethanes and the surface of thevulcanized tire to be coated.

The Applicant has faced the problem of providing a colored compositionwhich may be applied onto the surface of a vulcanized tire whichovercome all the disadvantages above disclosed.

The Applicant has now found that it is possible to overcome the abovedisclosed disadvantages by using a colored composition comprising atleast one crosslinked polymeric compound obtained from the reaction ofat least one thermoplastic polyurethane with at least onepolyisocyanate, at least one thermoplastic polymeric compounds having aglass transition temperature higher than or equal to 20° C., and atleast one coloring agent. Said colored composition allows to form acolored coating layer which is flexible and strongly adheres to thesurface of the vulcanized tire without previously chemically treatingsaid surface. Moreover, the rubbery behaviour of said colored coatinglayer makes it possible to withstand all the deformations experiencedafter the manufacture of the tire and, in particular, upon the inflationthereof and in its later use. Moreover, said colored coating layer doesnot show discoloration problems. Furthermore, said colored coating layershows a good appearance (i.e., the formation of defects during theapplication of said colored composition onto the surface of thevulcanized tire is avoided).

According to a first aspect, the present invention relates to a tirecomprising at least one outer structural element, wherein said at leastone outer structural element is at least partially coated by at leastone colored coating layer including a colored composition comprising:

-   (a) from 5% by weight to 50% by weight, preferably from 15% by    weight to 30%, by weight, with respect to the total weight of the    dry colored composition, of at least one crosslinked polymeric    compound obtained by reacting (a₁) at least one thermoplastic    polyurethane with (a₂) at least one polyisocyanate;-   (b) from 10% by weight to 80% by weight, preferably from 30% by    weight to 70% by weight, with respect to the total weight of the dry    colored composition, of at least one thermoplastic polymeric    compound having a glass transition temperature higher than or equal    to 20° C., preferably of from 30° C. to 150° C., more preferably of    from 45° C. to 100° C.;-   (c) from 3% by weight to 50% by weight, preferably from 4% by weight    to 30% by weight, with respect to the total weight of the dry    colored composition, of at least one coloring agent.

According to one preferred embodiment, the tire comprises:

-   -   a carcass structure of a substantially toroidal shape, having        opposite lateral edges associated with respective right-hand and        left-hand bead structures, said bead structures comprising at        least one bead core and at least one bead filler;    -   a belt structure applied in a radially external position with        respect to said carcass structure;    -   a tread band radially superimposed on said belt structure;    -   a pair of sidewalls applied laterally on opposite sides with        respect to said carcass structure;        wherein said at least one outer structural element is at least        one of said sidewalls;

According to a further aspect, the present invention relates to acolored composition comprising:

-   -   (a) from 5% by weight to 50% by weight, preferably from 15% by        weight to 30% by weight, with respect to the total weight of the        dry colored composition, of at least one crosslinked polymeric        compound obtained by reacting (a₁) at least one thermoplastic        polyurethane with (a₂) at least one polyisocyanate;    -   (b) from 10% by weight to 80% by weight, preferably from 30% by        weight to 70% by weight, with respect to the total weight of the        dry colored composition, of at least one thermoplastic polymeric        compound having a glass transition temperature higher than or        equal to 20° C., preferably of from 30° C. to 150° C., more        preferably of from 45° C. to 100° C.;    -   (c) from 3% by weight to 50% by weight, preferably from 4% by        weight to 30% by weight, with respect to the total weight of the        dry colored composition, of at least one coloring agent.

For the purpose of the present description and of the claims whichfollow, except where otherwise indicated, all numbers expressingamounts, quantities, percentages, and so forth, are to be understood asbeing modified in all instances by the term “about”. Also, all rangesinclude any combination of the maximum and minimum points disclosed andinclude any intermediate ranges therein, which may or may not bespecifically enumerated herein.

According to one preferred embodiment, said thermoplastic polyurethane(a₁) has a glass transition temperature (T_(g)) lower than or equal to−10° C., preferably of from −15° C. to −60° C.

According to a further preferred embodiment, said thermoplasticpolyurethane (a₁) has a softening point of from 25° C. to 150° C.,preferably of from 30° C. to 100° C.

According to a further preferred embodiment, said thermoplasticpolyurethane (a₁) has a cold crystallization temperature of from −20° C.to +10° C., preferably of from −10° C. to +0° C.

Said glass transition temperature (T_(g)), said softening point and saidcold crystallization temperature, were measured by DSC (DifferentialScanning Calorimetry) analysis: further details about said analysis willbe given in the examples which follow.

According to one preferred embodiment, said thermoplastic polyurethane(a₁) has a Standard Viscosity, measured at 20° C., of from 500 mPa·s to2000 mPa·s, preferably of from 1000 mPa·s to 1500 mPa·s.

Said Standard Viscosity was measured as a 15% solution of saidthermoplastic polyurethane (a₁) in methyl ethyl ketone (MEK).

According to one preferred embodiment, said thermoplastic polyurethane(a₁) may be selected from crosslinkable polyurethanes obtained byreacting one or more polyols with one or more organic polyisocyanates.As used herein, the term “crosslinkable” means that the polymer hasfunctional groups capable of reacting with a crosslinking agent.

Preferably, said thermoplastic polyurethane (a₁) has pendant hydroxylgroups free for reaction with a crosslinking agent, although otherfunctional groups are possible for crosslinking such as, for example,isocyanate groups, or carboxyl groups. Said functional groups areunprotected (i.e., unblocked), so as to allow crosslinking.

A variety of polyols may be utilized in preparing the thermoplasticpolyurethane (a₁). Also mixture of polyols may be used. The term“polyols” as used herein refers to polyhydric alcohols containing two ormore hydroxyl groups. The polyol preferably has a hydroxyl functionalityof 2-4 (i.e. diols, triols, tetraols). More preferably, the polyol is adiol, although higher functional polyols such as, for example, triols ortetrols, may be used in combination with a diol. Most preferably, thepolyol is a diol or a mixture of diols.

The polyol can be a polyether polyol such as, for example,polytetramethylene glycol, or polypropylene glycol; a polyester polyolsuch as, for example, the reaction product of adipic acid and neopentylglycol, or of phthalic anhydride and hexanediol; an acrylic polyol; ormixtures thereof.

According to one preferred embodiment, the polyol is a hydroxylterminated polyester polyol prepared by polycondensation of an aliphaticor aromatic dicarboxylic acid and a molar excess of an aliphatic glycol.

According to a further preferred embodiment, the polyol is a hydroxylterminated polyester diol of the following formula:

HO—[R—O—C(O)—R′—C(O)—O—R—O—]_(n)H

wherein R is an aliphatic group having from 2 to 10 carbon atoms, R′ isan aliphatic or aromatic group having up to 14 carbon atoms, and n is atleast 2. This polyester diol is typically formed from one or more typesof aliphatic or aromatic acids/esters and one or more types of aliphaticdiols. For example, a polyester diol of the above formula may beprepared from an aromatic acid or ester such as, for example,isophthalic acid, dimethyl isophthalate, or mixture thereof, and a diolsuch as, for example, neopentyl glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, or mixture thereof. If both an aromatic and an aliphaticmaterial are used, the weight percent of the aromatic material isgenerally less than that of the aliphatic material.

The polyester diol, or other suitable polyol, preferably has a hydroxylequivalent weight of from 90 to 5000, more preferably of from 200 to3000, and most preferably of from 250 to 2000. The polyester diol, orother suitable polyol, preferably has an acid number of no greater than1.0, and more preferably of no greater than 0.7. Acid number may bedetermined in accordance with ASTM Standard D4662-93.

Example of a polyester diol which may be used according to the presentinvention and is available commercially is the product known under thetradename of Fomrez® 8056-146 from Witco Corp. This resin is believed tocontain neopentyl glycol at approximately 26 wt %, 1,6-hexanediol atapproximately 29 wt %, adipic acid/ester at approximately 33 wt %, andisophthalic acid/ester at approximately 12 wt %. Other polyester diolsare commercially available under the tradenames of Fomrez 55-112(believed to contain approximately 47 wt % neopentyl glycol andapproximately 53% adipic acid/ester) and Fomrez® 8066-120 (believed tocontain approximately 49 wt % hexanediol, approximately 33 wt % adipicacid/ester, and approximately 18 wt % isophthalic acid/ester) from WitcoCorp, as well as Lexorez® from Inolex Chemical Company, or Rucoflex®from Ruco Polymer Corp. It should be understood that mixtures of suchdiols may be used in the preparation of the thermoplastic polyurethane(a₁) used according to the present invention.

Alternatively, a variety of triols may be utilized in the preparation ofsaid thermoplastic polyurethane (a₁).

According to one preferred embodiment, said triols may be selected frompolyether triols such as, for example, polypropylene oxide triol,polyester triols other than polycaprolactone triols, and simple triolssuch as, for example, trimethylolpropane, glycerol, or mixtures thereof.Preferably the hydroxyl groups in the triol are primary in order tofacilitate crosslinking of the resultant polymer.

Examples of triols which may be used according to the present inventionand are commercially available are the products known under thetradename of Fomrez® 1066 (trimethylolpropane, hexanediol, and adipate)from Witco Corp., Tone® 0305 (a polycaprolactone triol) from UnionCarbide Corp., Rucoflex® F-2311 from Ruco Polymer Corp. It should beunderstood that these materials could be used as mixtures with otherpolyols to achieve a glass transition temperature (T_(g)) of less than0° C.

Other polyester polyols are available from Bayer under the tradename ofDesmophen®. For example, Desmophen® 670 BA is available as a solution inn-butyl acetate (80% solids). It is believed to be derived from amixture comprising isophthalic acid, 1,6-hexanediol, trimethylolpropane, phtalic acid and/or phthalic anhydride, and is characterized ashaving an equivalent weight of 500, an acid number of 2.0 maximum, and ahydroxyl number of from 104 to 112.

Tetrafunctional or higher alcohols such as pentaerythritol may also beuseful polyols. If a triol and higher functional polyol is used, theNCO:OH stoichiometry will need to be adjusted accordingly, although thiswould be understood by anyone skilled in the art.

A wide variety of polyisocyanates may be utilized in preparing saidpolyurethane (a₁). As used herein, the term “polyisocyanates” means anyorganic compound that has two or more reactive isocyanate (—NCO) groupsin a single molecule that may be aliphatic, alicyclic, aromatic, ormixtures thereof. This definition includes diisocyanates,triisocyanates, tetraisocyanates, or mixtures thereof. Preferably,diisocyanates are utilized. These isocyanate groups may be bonded toaromatic or cycloaliphatic groups. Most preferably aliphaticisocyanates, including cycloaliphatic isocyanates, are used to improveweathering and eliminate yellowing. Useful diisocyanates include, butare not limited to, those selected from the group consisting ofbis(4-isocyanotecyclohexyl)methane (H₁₂ MDI, available from BayerCorp.), diphenylmethane diisocyanate (MDI, available from Bayer Corp.),isophorone diisocyanate (IPDI, available from Huels America), toluene2,4-diisocyanate (TDI, available from Aldrich Chemical Co.),hexamethylene diisocyanate (HDI, available from Aldrich Chemical Co.),m-tetramethylxylene diisocyanate (TMXDI, available from Aldrich ChemicalCo.), 1,3-phenylene diisocyanate. It is also noted that mixtures of theabove disclosed diisocyanates may also be used.

The stoichiometry of the polyurethane reaction is based on a ratio ofisocyanate equivalents to polyol equivalents (NCO:OH ratio). The overallpreferred NCO:OH ratio for the polyurethane is less than 1:1 to allowfor residual hydroxyl groups in the resultant polyurethane. Morepreferably, the NCO:OH ratio is from 0.8:1 to 1:1, still morepreferably, the NCO:OH ratio is of from 0.9:1 to 1:1. It will beunderstood by anyone skilled in the art that this ratio will varydepending upon the synthetic sequence when using triol(s) and/ortetrol(s). This is accomplished typically by varying the amount ofisocyanate such that gellation is avoided and a soluble product isobtained.

A catalyst may be added to the reaction mixture of polyol(s) andpolyisocyanate(s) to promote the reaction. Catalysts for reactingpolyisocyanate and active hydrogen containing compounds are well knownin the art. Examples of said catalysts may be found, for instance, inU.S. Pat. No. 4,495,061. Preferred catalysts include organometalliccompounds and amines. The organometallic compounds may be organotincompounds such as dimethyltin dilaurate, dibutyltin dilaurate, anddibutyltin dimercaptide. The preferred catalyst is dibutyltin dilaurate.The catalyst is used in an amount effective to promote the reaction.Preferably, it is used in an amount of from 0.01% by weight to 2% byweight, preferably of from 0.01% by weight to 0.03% by weight, withrespect to the total weight of solids.

Said thermoplastic polyurethane (a₁) may be prepared in the presence orabsence of a solvent. Preferably, it is prepared in the presence of oneor more organic solvents. Examples of suitable solvents include, but arenot limited to, methyl ethyl ketone, amyl acetate, benzene, toluene,butanone, butoxy ethoxyethyl acetate, 2-ethoxyethyl acetate,cyclohexanone, dioxane, 4-methyl-2-pentanone, tetrahydrofuran, benzene,toluene, xylene, or mixtures thereof. Methyl ethyl ketone isparticularly preferred. The polyurethane reaction mixture preferablyincludes from 30% by weight to 75% by weight, more preferably from 40%by weight to 55% by weight, of total solids.

According to one preferred embodiment, said thermoplastic polyurethane(a₁) is selected from hydroxyl terminated polyester polyurethanes.

Examples of thermoplastic polyurethanes (a₁) which may be used accordingto the present invention and are commercially available are the productsIrostic® from Huntsman Polyurethanes.

As reported above, in order to obtain the crosslinked polymeric compound(a) above disclosed, at least one polyisocyanate (a₂) may be used.

According to one preferred embodiment, said polyisocyanate (a₂) may beselected from the polyisocyanates above disclosed. Aromaticpolyisocyanates are particularly preferred.

Examples of polyisocyanates (a₂) which may be used according to thepresent invention and are commercially available are the productsIrodur® E 462 from Huntsman Polyurethanes, or Desmodur® MT from Bayer.

In the crosslinking reaction the molar ratio of the hydroxyl group ofthe thermoplastic polyurethane (a₁) and the isocyanate groups of thepolyisocyanate (a₂) may be different.

For example, when a hydroxyl terminated polyester polyurethane is usedas the thermoplastic polyurethane (a₁) and a polyisocyanate (a₂) is usedas the crosslinking agent, the molar ratio of the hydroxyl group of thehydroxyl terminated polyester polyurethane to the isocyanate group ofthe polyisocyanate is preferably of from 1:10 to 10:1, more preferablyof from 1.1:1 to 2:1.

A catalyst may also be added to promote the crosslinking reaction.Suitable catalysts may be selected from those above disclosed.

The crosslinking reaction may be carried out at a temperature of from20° C. to 120° C., for a time of from 10 minutes to 72 hours.

For example, the crosslinking may be carried out by heating thethermoplastic polyurethane (a₁) and the polyisocyanate (a₂) at atemperature of from 50° C. to 120° C., preferably of from 40° C. to 80°C., for a time of from 10 minutes to 6 hours, preferably of from 30minutes to 2 hours.

Alternatively, the crosslinking reaction may be carried out at roomtemperature (23° C.), for a time of from 24 hours to 72 hours,preferably of from 26 hours to 48 hours.

Preferably, in order to avoid an excessive increase of the viscosity ofthe colored composition before the application of the same onto thesurface to be coated, the mixing of the thermoplastic polyurethane (a₁)and the polyisocyanate (a₂) is carried out not more than 48 hours,preferably from 5 minutes to 24 hours, before the step of applying saidcolored composition onto the surface to be coated.

The above crosslinking reaction may be carried out either before theaddition of components (b) and (c) to the colored composition, or afterthe addition of components (b) and (c) to the colored composition.Preferably, the above crosslinking reaction is carried out after theaddition of components (b) and (c) to the colored composition.

Preferably, the above crosslinking reaction is carried out after thestep of applying said colored composition onto the surface to be coated.

According to one preferred embodiment, said thermoplastic polymericcompound (b) contains hydroxyl groups in its molecule, said hydroxylgroups being present in an amount higher than or equal to 1% by weight,preferably of from 1.5% by weight to 20% by weight, with respect to thetotal weight of the thermoplastic polymeric compound (b).

Said hydroxyl groups may be present both in the main chain of thethermoplastic polymeric compound and/or in its side chain.

According to a further preferred embodiment, said thermoplasticpolymeric compound (b) is selected from:

-   (b₁) vinyl chloride copolymers;-   (b₂) hydrogenated polyketones;    or mixtures thereof.

According to one preferred embodiment, said vinyl chloride copolymers(b₁) may be selected from copolymers of vinyl chloride with at least oneother vinyl comonomer.

The term copolymer as used herein includes copolymers of vinyl chloridewith two or more comonomers, and thus includes terpolymers.

Preferably, the vinyl chloride copolymers (b₁) may be prepared bycopolymerizing vinyl chloride with at least one vinyl comonomer whichmay be selected from: vinyl acetate, vinyl alcohol, 2-propenyl acetate,acrylic acid, acrylic acid esters (such as, for example, methylmethacrylate, 2-hydroxypropyl acrylate, glycidyl methacrylate), isobutylvinyl ether, maleic acid, vinyl stearate, acrylamide, vinyl sulfonicacid, vinylidene chloride, or mixtures thereof.

Vinyl chloride/acrylic acid ester copolymers, vinyl chloride/vinylacetate copolymers, or mixtures thereof, are particularly preferred.

Said vinyl chloride copolymers (b₁) may further contain carboxylicand/or epoxy functional groups in their molecule.

Alternatively, said vinyl chloride copolymers (b₁) comprise terpolymersof vinyl chloride, another vinyl compound such as vinyl acetate, and anunsaturated carboxylic or polycarboxylic acid or ester. Some examples ofuseful terpolymers include vinyl chloride/vinyl acetate/maleic acidterpolymers, vinyl chloride/vinyl acetate/acrylic acid terpolymers,vinyl chloride/vinyl acetate/crotonic acid terpolymers, or mixturethereof.

Said vinyl chloride copolymers (b₁) may be obtained commercially or maybe synthesized by a free radical initiated polymerization of vinylchloride, at least one other vinyl comonomer and, optionally, at leastone unsaturated carboxylic or polycarboxylic acid or ester.

Examples of vinyl chloride copolymers (b₁) which may be used accordingto the present invention and are commercially available are the productsVinnol® from Waker.

According to one preferred embodiment said hydrogenated polyketones (b₂)may be selected from compounds having the following general formula (I):

wherein:

-   -   R groups, which may be equal or different from each other,        represent a linear or branched C₁-C₂₀ alkyl group; a C₆-C₁₈ aryl        group;    -   the n:m ratio is of from 0.1:1 to 1:1, preferably of from 0.3:1        to 0.5:1.

Example of compounds having general formula (I) which may be usedaccording to the present invention are: hydrogenated poly(vinyl methylketone), hydrogenated poly(vinyl butyl ketone), hydrogenated poly(vinylphenyl ketone), hydrogenated poly(vinyl naphthyl ketone), or mixturesthereof. Hydrogenated poly(vinyl phenyl ketone) is particularlypreferred.

According to one preferred embodiment, said coloring agent (c) may beselected from: iron oxide, titanium dioxide, mica, calcium sodiumborosilicate, powdered metals such as powdered aluminum or copper, metalpastes such as aluminum pastes, organic constituent containing.pigments, inorganic constituent containing pigments, fluorescentconstituent containing pigments, phosphorescent constituent containingpigments, luminescent constituent containing pigments, ultravioletabsorbing pigments, mineral constituent containing pigments, amorphousglass oxides, polyacrylates, metal flakes, reflective pigments, ormixtures thereof.

The selection of the coloring agent (c) varied based upon the colorchoice and intensity of color one wishes to impart onto the surface tobe coated.

Examples of coloring agent (c) which may be used according to thepresent invention and are commercially available are the productsOffset® FM/4500 (aluminum paste) from Schlenk, or Hostaperm Blue®BT-617-D (blue pigment) from Clariant.

Reinforcing fillers such as, for example, carbon black or silica, may beadded to the colored composition above disclosed to impart otherproperties to said colored composition, as long as the color of thefiller does not modify or adversely change the desired coloration of thecolored composition. The presence of carbon black in very smallproportion, i.e. a few phr [phr=parts per hundred part of thermoplasticpolyurethane (a₁)], allows one to obtain a colour with a darkerappearance, especially with red, blue, or green pigments.

The above disclosed colored composition may be applied onto the surfaceof the outer structural element of a vulcanized tire. Preferably, asreported above, the crosslinking reaction between the thermoplasticpolyurethane (a₁) and the polyisocyanate (a₂) is carried out after theapplication of said colored composition onto the surface of the outerstructural element of a vulcanized tire.

The method of applying said colored composition onto the surface of theouter structural element of a vulcanized tire comprises the followingsteps:

-   -   (i) cleaning a portion of the surface to be coated with a        solvent;    -   (ii) coating said surface with the colored composition above        disclosed;    -   (iii) drying said colored composition to obtain a colored        coating layer.

Preferably, the solvent used in step (i) may be selected from: ketonessuch as, for example, acetone, methyl ethyl ketone, methyl isobutylketone; alcohols such as, for example, methanol, ethanol, isopropanol,butanol; aliphatic or aromatic hydrocarbons such as, for example,pentane, hexane, benzene, toluene; or mixture thereof.

The above disclosed step (ii) may be carried out with techniques knownin the art such as, for example, by painting, brushing, spraying,rolling, dipping, scraping, pad printing.

The above disclosed step (iii) may be carried out in different ways.

For example, the above reported step (iii) may be carried out at ambienttemperature (23° C.), for a time of from 24 hours to 72 hours,preferably of from 26 hour to 48 hours.

Alternatively, the above reported step (iii) may be carried out byheating the vulcanized tire at a temperature of from 50° C. to 120° C.,preferably of from 40° C. to 80° C., for a time of from 10 minutes to 6hours, preferably of from 30 minutes to 2 hours.

During said step (iii), the crosslinking of the polymeric compound (a)is obtained.

Depending on the means used to deposit the colored composition, thethickness of the colored coating layer formed after drying said coloredcomposition may be varied. Good results are obtained with a dry coloredcoating layer having a thickness higher than or equal to 20 μm.

However, the desired thickness may vary according to the surface wherethe colored composition is applied.

For example, a thickness of from 20 μm to 100 μm, may be sufficient onthe tire sidewalls as, a higher thickness such as, for example, of from100 μm to 500 μm, may be required for the bottoms of the grooves of thetread patterns of the tire, or in the zones where a protective effect ofthe colored coating layer is required with respect to the atmosphere.

The tire may or may not be mounted and inflated prior to saidapplication.

The outer structural element of the tire which has to be coated isusually obtained by crosslinking a crosslinkable elastomeric compositioncomprising at least one elastomeric polymer. Preferably, saidelastomeric polymer may be selected from: cis-1,4-polyisoprene (naturalor synthetic, preferably natural rubber), 3,4-polyisoprene,polybutadiene (in particular polybutadiene with a high 1,4-cis content),optionally halogenated isoprene/isobutene copolymers,1,3-butadiene/acrylonitrile copolymers, styrene/1,3-butadienecopolymers, styrene/isoprene/1,3-butadiene copolymers,styrene/1,3-butadiene/acrylonitrile copolymers, ethylene/propylenecopolymers (EPR) or ethylene/propylene/diene copolymers (EPDM);polyisobutene; butyl rubbers; halobutyl rubbers, in particularchlorobutyl or bromobutyl rubbers; or mixtures thereof.

Said crosslinkable elastomeric composition may further comprise at leastone reinforcing filler such as, for example, carbon black, silica,alumina, aluminosilicates, calcium carbonate, kaolin, or mixturesthereof.

The crosslinkable elastomeric composition above disclosed may bevulcanized according to known techniques, in particular withsulfur-based vulcanizing systems commonly used for elastomeric polymers.To this end, in the crosslinkable composition, after one or more stepsof thermomechanical processing, a sulfur-based. vulcanizing agent isincorporated together with vulcanization accelerators. In the finalprocessing step, the temperature is generally kept below 140° C., so asto avoid any unwanted pre-crosslinking phenomena.

The vulcanizing agent most advantageously used is sulfur, or moleculescontaining sulfur (sulfur donors), with accelerators and activatorsknown to those skilled in the art.

Activators that are particularly effective are zinc compounds, and inparticular ZnO, ZnCO₃, zinc salts of saturated or unsaturated fattyacids containing from 8 to 18 carbon atoms, such as, for example, zincstearate, which are preferably formed in situ in the elastomericcomposition from ZnO and fatty acid, and also BiO, PbO, Pb₃O₄, PbO₂, ormixtures thereof.

Accelerators that are commonly used may be selected from:dithiocarbamates, guanidine, thiourea, thiazoles, sulphenamides,thiurams, amines, xanthates, or mixtures thereof.

Said crosslinkable. elastomeric composition may comprise other commonlyused additives selected on the basis of the specific application forwhich the composition is intended. For example, the following may beadded to said crosslinkable elastomeric composition: antioxidants,anti-ageing agents, plasticizers, adhesives, anti-ozone agents,modifying resins, fibres (for example Kevlar® pulp), or mixturesthereof.

The present invention will now be illustrated in further detail by meansof the attached FIG. 1 which is a side view of a tire made according tothe present invention.

FIG. 1 shows a tire (10) having a sidewall (11) to which a coloredcomposition according to the present invention is applied. In FIG. 1,the obtained colored coating layer is circumferentially extended tocover the whole sidewall (11). Alternatively, the colored coating layermay cover only a portion of the tire sidewall, such as for example, inthe case said colored coating layer covers designs, letters, logos,trademarks, decals which may be placed upon the sidewall of the tire.

The process for producing the tire according to the present inventionmay be carried out according to techniques and using apparatus that areknown in the art, as described, for example, in European Patents EP199,064, or in U.S. Pat. No. 4,872,822 or U.S. Pat. No. 4,768,937, saidprocess including manufacturing the crude tire, moulding and vulcanizingthe crude tire.

The present invention will be further illustrated below by means of anumber of preparation examples, which are given for purely indicativepurposes and without any limitation of this invention.

The components used for the preparation of the colored composition werethe following:

-   Irostic®S 6148-12 (Huntsman Polyurethanes): hydroxyl terminated    polyester polyurethane having a glass transition temperature of    −47° C. (midpoint); a softening point of 38° C. (peak); a cold    crystallization temperature of −8° C. (peak); a Standard viscosity,    measured at 20° C., as a 15% solution of said polyurethane in methyl    ethyl ketone (MEK), of 1000 mPa·s;-   Irodur® E 462 (Huntsman Polyurethanes): 27% ethyl acetate solution    of aromatic polyisocyanate;-   Vinnol® E 15/48 A: vinyl chloride/acrylic acid ester copolymer    having a glass transition temperature of +69° C.; a hydroxyl groups    contents of 1.8% by weight with respect to the total weight of the    copolymer;-   PVPK (Sigma Aldrich): hydrogenated poly(vinyl phenyl ketone) having    a glass transition temperature of 50° C.; a hydroxyl groups contents    of 12.7% by weight with respect to the total weight of the polymer.-   Offset® FM/4500 (Schlenk); aluminium paste.

The glass transition temperature, the softening point, and the coldcrystallization temperature of the Irostic®S 6148-12, were determined byDSC (Differential Scanning Calorimetry) using a Mettler Toledo DSC 820differential scanning calorimeter. The temperature program below wasapplied to the sample to be analysed:

-   -   isothermal for 5 minutes at +50° C.;    -   cooling from +50° C. to −130° C. at a rate of 10° C./min.;    -   isothermal for 10 minutes at −130° C.;    -   heating from −130° C. to 150° C. at a rate of 10° C./min.

EXAMPLE 1 Preparation of the Colored Composition

45 g of a 10% by weight solution of Irostic® S 6148-12 in methyl ethylketone, 45 g of a 25% by weight solution of Vinnol® E 15/48 A in methylethyl ketone, 10 g of Irodur® E 462, and 1.0 g of Offset® FM/4500, wereadded to a 250 ml flask and were maintained, under stirring, for 10 min,at a temperature of 30°. A colored composition was so obtained.

EXAMPLE 2 Preparation of the Colored Composition

30 g of a 10% by weight solution of Irosticφ S 6148-12 in methyl ethylketone, 35 g of a 20% by weight solution of hydrogented poly(vinylphenyl ketone) in methyl ethyl ketone, 10 g of Irodur® E 462, and 1.0 gof Offset® FM/4500, were added to a 250 ml flask and were maintained,under stirring, for 10 min, at a temperature of 30° C. A coloredcomposition was so obtained.

EXAMPLE 3 (COMPARATIVE) Preparation of the Colored Composition

100 g of a 10% by weight solution of Irostic® S 6148-12 in methyl ethylketone, 10 g of Irodur E 462, and 1.0 g of Offset® FM/4500, were addedto a 250 ml flask and were maintained, under stirring, for 10 min, at atemperature of 30° C. A colored composition was so obtained.

EXAMPLE 4 Xenon-ARC Accelerated Test

An elastomeric composition as disclosed in Table 1 was prepared asfollows [the amounts of the various components are given in phr(phr=part per hundred parts of rubber)].

All the components, except sulfur, retardant (PVI) and accelerator(CBS), were mixed together in an internal mixer (model Pomini PL 1.6)for about 5 min (1^(st) Step). As soon as the temperature reached 145±5°C., the elastomeric composition was discharged. The sulfur, retardant(PVI) and accelerator (CBS), were then added and mixing was carried outin an open roll mixer (2^(nd) Step).

TABLE 1 EXAMPLE 3 1^(st) STEP NR 50 BR 50 N660 50 Zinc oxide 3 Stearicacid 2 Microcrystalline wax 2 6-PPD 4 2^(nd) STEP CBS 0.80 PVI 0.20Sulfur 1.80 (*) comparative. NR: natural rubber; BR:cis-1,4-polybutadiene (Europrene ® Neocis BR40 - Polimeri Europa); N660:carbon black; 6-PPD:N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylene-diamine; CBS (accelerator):N-cyclohexyl-2-benzothiazyl sulphenamide (Vulkacit ® CZ - Bayer); PVI(retardant): N-cyclohexylthiophthalimide (Santogard ® PVI - Monsanto).

Test pieces of the above disclosed crosslinked elastomeric compositions(vulcanized at 170° C. for 10 min) having the following dimensions 100mm×40 mm'3 mm were obtained.

The obtained test pieces were washed with methyl ethyl ketone andsubsequently coated with the colored composition of Example 1, 2 and 3,by means of a brush. The colored composition was let to dry, at roomtemperature (23° C.), for 20 minutes and, subsequently, in an oven, at80° C., for 2 hours. After drying, a colored coating layer 50 μm thickwas obtained.

The colored test pieces were subjected to Xenon-Arc Accelerated Testaccording to ASTM Standard D6695-03 using a Q-Sun Xe-1-S (Xenon TestChamber with daylight filter). The following conditions were applied:

-   -   black panel temperature: 60° C. (light cycle);    -   irradiance level: 0.55 W/m² at 340 nm;        -   intermitted light/dark cycle was: 160 min light, 5 min dark,            without water spraying.

After 16 hours at the conditions reported above, the test pieces wereexamined visually in order to determine the presence of staining. Theobtained results are the following:

-   -   test pieces coated with a colored composition of Example 1: no        detectable staining;    -   test pieces coated with a colored composition of Example 2: no        detectable staining;    -   test pieces coated with a colored composition of Example 3        (comparative): remarkable staining.

Moreover, the above reported test pieces were manually scratched with ascraper in order to evaluate the adhesion of the colored coating layerto the rubber surface: all the three test pieces showed good adhesion.

1-46. (canceled)
 47. A tire comprising at least one outer structuralelement, wherein said at least one outer structural element is at leastpartially coated by at least one colored coating layer comprising acolored composition comprising: (a) 5% by weight to 50% by weight withrespect to the total weight of the dry colored composition of at leastone crosslinked polymeric compound obtained by reacting (a₁) at leastone thermoplastic polyurethane with (a₂) at least one polyisocyanate;(b) 10% by weight to 80% by weight with respect to the total weight ofthe dry colored composition of at least one thermoplastic polymericcompound having a glass transition temperature higher than or equal to20° C.; and (c) 3% by weight to 50% by weight with respect to the totalweight of the dry colored composition of at least one coloring agent.48. The tire according to claim 47, comprising: a carcass structure of asubstantially toroidal shape, having opposite lateral edges associatedwith respective right-hand and left-hand bead structures, said beadstructures comprising at least one bead core and at least one beadfiller; a belt structure applied in a radially external position withrespect to said carcass structure; a tread band radially superimposed onsaid belt structure; and a pair of sidewalls applied laterally onopposite sides with respect to said carcass structure, wherein said atleast one outer structural element is at least one of said sidewalls.49. The tire according to claim 47, wherein said colored compositioncomprises 15% by weight to 30% by weight with respect to the totalweight of the dry colored composition of at least one crosslinkedpolymeric compound (a).
 50. The tire according to claim 47, wherein saidcolored composition comprises 30% by weight to 70% by weight withrespect to the total weight of the dry colored composition of at leastone thermoplastic polymeric compound (b).
 51. The tire according toclaim 47, wherein said colored composition comprises 4% by weight to 30%by weight with respect to the total weight of the dry coloredcomposition of at least one coloring agent (c).
 52. The tire accordingto claim 47, wherein said thermoplastic polymeric compound (b) has aglass transition temperature of 30° C. to 150° C.
 53. The tire accordingto claim 52, wherein said thermoplastic polymeric compound (b) has aglass transition temperature of 45° C. to 100° C.
 54. The tire accordingto claim 47, wherein said thermoplastic polyurethane (a₁) has a glasstransition temperature (T_(g)) lower than or equal to −10° C.
 55. Thetire according to claim 54, wherein said thermoplastic polyurethane (a₁)has a glass transition temperature (T_(g)) of −15° C. to −60° C.
 56. Thetire according to claim 47, wherein said thermoplastic polyurethane (a₁)has a softening point of 25° C. to 150° C.
 57. The tire according toclaim 56, wherein said thermoplastic polyurethane (a₁) has a softeningpoint of 30° C. to 100° C.
 58. The tire according to claim 47, whereinsaid thermoplastic polyurethane (a₁) has a cold crystallizationtemperature of −20° C. to +10° C.
 59. The tire according to claim 58,wherein said thermoplastic polyurethane (a₁) has a cold crystallizationtemperature of −10° C. to +0° C.
 60. The tire according to claim 47,wherein said thermoplastic polyurethane (a₁) has a standard viscosity,measured at 20° C., of 500 mPa·s to 2000 mPa·s.
 61. The tire accordingto claim 60, wherein said thermoplastic polyurethane (a₁) has a standardviscosity, measured at 20° C., of 1000 mPa·s to 1500 mPa·s.
 62. The tireaccording to claim 47, wherein said thermoplastic polyurethane (a₁) isselected from hydroxyl terminated polyester polyurethanes.
 63. The tireaccording to claim 47, wherein said polyisocyanate (a₂) is selected fromaromatic polyisocyanates.
 64. The tire according to claim 47, whereinsaid thermoplastic polymeric compound (b) comprises hydroxyl groups,said hydroxyl groups being present in an amount greater than or equal to1 % by weight with respect to the total weight of the thermoplasticpolymeric compound (b).
 65. The tire according to claim 64, wherein saidsaid hydroxyl groups are present in an amount of 1.5% by weight to 20%by weight with respect to the total weight of the thermoplasticpolymeric compound (b).
 66. The tire according to claim 47, wherein saidthermoplastic polymeric compound (b) is selected from: (b₁) vinylchloride copolymers; (b₂) hydrogenated polyketones; or mixtures thereof.67. The tire according to claim 66, wherein said vinyl chloridecopolymers (b₁) are selected from copolymers of vinyl chloride with atleast one other vinyl comonomer.
 68. The tire according to claim 67,wherein said vinyl comonomer is selected from: vinyl acetate, vinylalcohol, 2-propenyl acetate, acrylic acid, acrylic acid esters, methylmethacrylate, 2-hydroxypropyl acrylate, glycidyl methacrylate, isobutylvinyl ether, maleic acid, vinyl stearate, acrylamide, vinyl sulfonicacid, vinylidene chloride, or mixtures thereof.
 69. The tire accordingto claim 66, wherein said vinyl chloride copolymers (b₁) are selectedfrom vinyl chloride/acrylic acid ester copolymers, vinyl chloride/vinylacetate copolymers, or mixtures thereof.
 70. The tire according to claim66, wherein said vinyl chloride copolymers (b₁) comprise carboxylicand/or epoxy functional groups.
 71. The tire according to claim 66,wherein said vinyl chloride copolymers (b₁) comprise terpolymers ofvinyl chloride, another vinyl compound or vinyl acetate, and anunsaturated carboxylic or polycarboxylic acid or ester.
 72. The tireaccording to claim 71, wherein said terpolymers comprise vinylchloride/vinyl acetate/maleic acid terpolymers; vinyl chloride/vinylacetate/acrylic acid terpolymers, vinyl chloride/vinyl acetate/crotonicacid terpolymers or mixtures thereof.
 73. The tire according to claim66, wherein said hydrogenated polyketones (b₂) are selected fromcompounds having the following general formula (I):

wherein: R groups, which may be the same or different from each other,represent a linear or branched C₁-C₂₀ alkyl group; a C₆-C₁₈ aryl group;and the n:m ratio is 0.1:1 to 1:1, or 0.3:1 to 0.5:1.
 74. The tireaccording to claim 73, wherein said compounds having general formula (I)are: hydrogenated poly(vinyl methyl ketone), hydrogenated poly(vinylbutyl ketone), hydrogenated poly(vinyl phenyl ketone), hydrogenatedpoly(vinyl naphthyl ketone), or mixtures thereof.
 75. The tire accordingto claim 74, wherein said compounds having general formula (I) arehydrogenated poly(vinyl phenyl ketones).
 76. The tire according to claim47, wherein said coloring agent (c) is selected from iron oxide,titanium dioxide, mica, calcium sodium borosilicate, powdered metals,powered aluminum or powdered copper, metal pastes, aluminum pastes,organic constituent containing pigments, inorganic constituentcontaining pigments, fluorescent constituent containing pigments,phosphorescent constituent containing pigments, luminescent constituentcontaining pigments, ultraviolet absorbing pigments, mineral constituentcontaining pigments, amorphous glass oxides, polyacrylates, metalflakes, reflective pigments, or mixtures thereof.
 77. A coloredcomposition comprising: (a) 5% by weight to 50% by weight with respectto the total weight of the dry colored composition of at least onecrosslinked polymeric compound obtained by reacting (a₁) at least onethermoplastic polyurethane with (a₂) at least one polyisocyanate; (b)10% by weight to 80% by weight with respect to the total weight of thedry colored composition of at least one thermoplastic polymeric compoundhaving a glass transition temperature higher than or equal to 20° C.;and (c) 3% by weight to 50% by weight with respect to the total weightof the dry colored composition of at least one coloring agent.
 78. Thecolored composition according to claim 77, comprising 15% by weight to30% by weight with respect to the total weight of the dry coloredcomposition of at least one crosslinked polymeric compound (a).
 79. Thecolored composition according to claim 77, comprising 30% by weight to70% by weight with respect to the total weight of the dry coloredcomposition of at least one thermoplastic polymeric compound (b). 80.The colored composition according to claim 77, comprising 4% by weightto 30% by weight with respect to the total weight of the dry coloredcomposition of at least one coloring agent (c).
 81. The coloredcomposition according to claim 77, wherein said thermoplastic polymericcompound (b) has a glass transition temperature of 30° C. to 150° C. 82.The colored composition according to claim 81, wherein saidthermoplastic polymeric compound (b) has a glass transition temperatureof 45° C. to 100° C.
 83. The colored composition according to claim 77,wherein said thermoplastic polyurethane (a₁): has a glass transitiontemperature (T_(g)) lower than or equal to −10° C.; or has a softeningpoint of 25° C. to 150° C.; or has a cold crystallization temperature of−20° C. to +10° C.; or has a standard viscosity, measured at 20° C., of500 mPa·s to 2000 mPa·s; or is selected from hydroxyl terminatedpolyester polyurethanes.
 84. The colored composition according to claim77, wherein said polyisocyanate (a₂) is selected from aromaticpolyisocyanates.
 85. The colored composition according to claim 77,wherein said thermoplastic polymeric compound (b): comprises hydroxylgroups, said hydroxyl groups being present in an amount higher than orequal to 1 % by weight with respect to the total weight of thethermoplastic polymeric compound (b); or is selected from: (b₁) vinylchloride copolymers; (b₂) hydrogenated polyketones; or mixtures thereof;or vinyl chloride copolymers (b₁) selected from copolymers of vinylchloride with at least one other vinyl comonomer; or vinyl chloridecopolymers (b₁) selected from vinyl chloride/acrylic acid estercopolymers, vinyl chloride/vinyl acetate copolymers, or mixturesthereof; or vinyl chloride copolymers (b₁) containing carboxylic and/orepoxy functional groups; or vinyl chloride copolymers (b₁) comprisingterpolymers of vinyl chloride, another vinyl compound, vinyl acetate,and an unsaturated carboxylic or polycarboxylic acid or ester; orhydrogenated polyketones (b₂) selected from compounds having thefollowing general formula (I):

wherein: R groups, which may be the same or different from each other,represent a linear or branched C₁-C₂₀ alkyl group; a C₆-C₁₈ aryl group;and the n: m ratio is 0.1 to 1:1, or 0.3:1 to 0.5:1.
 86. The coloredcomposition according to claim 77, wherein said coloring agent (c) isselected from iron oxide, titanium dioxide, mica, calcium sodiumborosilicate, powdered metals, powdered aluminum, powdered copper, metalpastes, aluminum pastes, organic constituent containing pigments,inorganic constituent containing pigments, fluorescent constituentcontaining pigments, phosphorescent constituent containing pigments,luminescent constituent containing pigments, ultraviolet absorbingpigments, mineral constituent containing pigments, amorphous glassoxides, polyacrylates, metal flakes, reflective pigments, or mixturesthereof.
 87. A method of applying the colored composition of claim 77onto the surface of an outer structural element of a vulcanized tirecomprising the following steps: (i) cleaning a portion of the surface tobe coated with a solvent; (ii) coating said surface with said coloredcomposition; and (iii) drying said colored composition to obtain acolored coating layer.
 88. The method according to claim 87, wherein thesolvent used in step (i) is selected from: ketones, acetone, methylethyl ketone, methyl isobutyl ketone; alcohols, methanol, ethanol,isopropanol, butanol; aliphatic or aromatic hydrocarbons, pentane,hexane, benzene, toluene; or mixture thereof.
 89. The method accordingto claim 87, wherein step (ii) is carried out by painting, brushing,spraying, rolling, dipping, scraping, or pad printing.
 90. The methodaccording to claim 87, wherein step (iii) is carried out at ambienttemperature for 24 hours to 72 hours.
 91. The method according to claim87, wherein step (iii) is carried out at a temperature of 50° C. to 120°C., for 10 minutes to 6 hours.
 92. The method according to claim 87,comprising crosslinking polymeric compound (a) during step (iii).